Binder composites based on hydrogenated nitrile rubbers and polycondensates for electrochemical energy storage devices

Abstract

The invention relates to a binder composite for a binder for an electrode of an electrochemical energy storage device, containing a) a hydrogenated nitrile rubber; and b) a polycondensate selected from the group consisting of polyamides having a melting point of 140 DEG C to 270 DEG C and polyesters having a melting point of 175 DEG C to 270 DEG C; wherein the polycondensate forms domains in the hydrogenated nitrile rubber, wherein the domains have a size D50% of less than 3 microns within the matrix of the hydrogenated nitrile rubber.

Description

[0001] This invention relates to binder composite materials that can be used in electrodes of electrochemical energy storage devices such as lithium-ion secondary batteries (LiB). The invention further relates to electrodes (such as cathodes) comprising such composite materials and electrochemical energy storage devices comprising the corresponding electrodes.

[0002] Lithium-ion rechargeable batteries have been widely used as a power source for portable devices since their introduction around 1991 as small, lightweight, and high-capacity batteries. In recent years, demand has increased significantly due to their use in electric vehicles.

[0003] The cathode of LiB mainly consists of cathode active material, which accounts for more than 95 wt% of all solid materials used therein.

[0004] The active material of the cathode in a lithium-ion battery allows lithium ions to reversibly insert into and extract from the cathode, while also allowing changes in the oxidation state of transition metal ions contained in the active material. The higher the mass fraction of this active material in the cathode, the higher its charge / discharge capacity, and subsequently, the higher its energy density.

[0005] Furthermore, the conductive materials used in the cathode and anode are essentially various allotropes of high-purity carbon, ranging from carbon black to carbon nanotubes to graphene.

[0006] Because these materials are solid powders, a flexible polymer binder is required to allow coating onto the current collector as a sufficiently stable layer. This layer can be further processed by cutting, slicing, and winding it together with the anode film to form the desired cell geometry. Since the uniformity of the coating and the uniform distribution of all materials are extremely important for battery performance, good dispersion of all particles must be ensured.

[0007] Fluorinated polymers have long been used to bind the particulate components of LiB electrodes (such as cathodes). The most common type of binder is based on polyvinylidene fluoride (PVDF), which may sometimes contain other monomer units. Some PVDF grades have very high molecular weights (Mw) to improve binding efficiency. PVDF exhibits low swelling in battery electrolytes, which is considered important for the integrity of the binder film during battery use.

[0008] However, using PVDF as a binder presents problems when selecting active materials with highly active alkaline components on their surfaces. This may be the case for nickel-rich active materials, such as nickel-cobalt-manganese oxides and nickel-cobalt-aluminum oxides in their lithiated forms. The strongly alkaline surface may induce defluorination of PVDF, leading to gelation of the polymer.

[0009] Nitrile butadiene rubber, especially its more electrochemically stable hydrogenated form (HNBR), has proven to be a suitable dispersant for all types of carbon materials, including carbon-coated active materials such as lithium iron phosphate (LPF-C). Insufficient dispersion can lead to gelation and agglomeration of conductive materials. Examples of using different grades of HNBR as dispersants can be found in EP 3319151, EP 3348582, KR 20150016852, EP 3358651, JP 6933285, JP2020194625, KR 20150067049, and EP 3355392. Conductive materials are used as an important component in electrodes to enable electrical conduction. Hydrogenated nitrile butadiene rubber is a very suitable polymer dispersant for dispersing nanoscale carbon materials in organic solvents to produce cathode slurries.

[0010] Examples of HNBR's use as an adhesive are found in US 2018 / 0183064, EP 2660980, EP 3240069, EP3276713, WO 2020 / 206606, and EP 3220461. HNBR can be used as a sole adhesive or as a co-adhesive with PVDF.

[0011] KR 102329520B1 proposes that while replacing a portion of PVDF with HNBR, a small amount of organic diacid, such as oxalic acid, be added to reduce gelling.

[0012] In the case of LPF-C (carbon-coated LFP), PVDF can be combined with HNBR to allow for better dispersion of small-sized carbon-coated LFP-C particles. Gelation of PVDF can still occur because it can release HF.

[0013] Compared to PVDF as a single binder, the main function of HNBR as a binder or co-binder in cathode slurries is to reduce viscosity, which is important for efficient coating steps on current collectors. Lower viscosity allows for increased solids content in the slurry, reducing the amount of process solvent to be evaporated and thus saving energy. However, the reasons for the viscosity reduction are not fully understood; one aspect may be the lower molecular weight of HNBR compared to PVDF for cell grades.

[0014] The viscosity of a cathode slurry depends on the formulation chosen. The active material typically comprises over 95% of all solids. Particle size, shape, and distribution can vary considerably. In the case of NCM (Ni, Co, and Mn-based oxides), the particles are spherical with considerably larger sizes, up to 10 micrometers. Therefore, slurries with NCM can be used at high solids contents. In the case of LFP (lithium iron phosphate), the particles can be much smaller, below the micrometer scale. They are mostly coated with a thin carbon layer, causing the particles to tend to agglomerate, and thus the typical solids content is much lower. The conductive material can be carbon black of various particle sizes and structures, and can be single-walled or multi-walled, bundled, or entangled carbon nanotubes. High dispersion of the conductive material is required. It is assumed that HNBR helps disperse the carbon material and prevents re-agglomeration, thereby reducing viscosity. The binder polymer itself can contribute to slurry viscosity, but the disadvantage is the high molecular weight required for PVDF.

[0015] Therefore, existing technological solutions still offer room for improvement.

[0016] Purpose of the invention

[0017] The object of this invention is to provide an adhesive for electrodes that at least partially overcomes one of the problems of the prior art. In particular, the object of this invention is to provide an adhesive for electrodes in electrochemical energy storage devices that has low viscosity and high solids content and is advantageous in terms of sustainability.

[0018] means to achieve an objective

[0019] These objectives are achieved, at least in part, by the adhesive composite material having the features of claim 1. The aforementioned objectives are further achieved by the electrode having the features of claim 12 and the electrochemical energy storage device having the features of claim 13. Preferred embodiments of the invention are described in the dependent claims, the specification, or the drawings, wherein additional features described or shown in the dependent claims, the specification, or the drawings may constitute the object of the invention individually or in any combination, unless the context clearly indicates otherwise.

[0020] A binder composite material for use as an electrode, preferably a cathode, in an electrochemical energy storage device is described, the binder composite material containing...

[0021] a) Hydrogenated nitrile butadiene rubber (HNBR); and

[0022] b) Condensation polymers selected from the group consisting of: polyamides (PA) having a melting point of 140°C to 270°C and polyesters having a melting point of 175°C to 270°C;

[0023] in

[0024] The condensate forms domains in the hydrogenated nitrile butadiene rubber, wherein these domains have a size D50 of less than 3 micrometers (µm) within the HNBR matrix.

[0025] When used as a binder material in electrodes, particularly cathodes, this composite material demonstrates significant advantages over existing technological solutions.

[0026] Surprisingly, adhesives containing hydrogenated nitrile butadiene rubber as a polymer matrix can provide excellent properties, with the polymer matrix having domains formed of polyamide having defined dimensions as outlined above.

[0027] Until now, the use of condensation polymers such as polyamides within battery cells has been limited to PA nanofibers as part of the separator layer (M. Yanilmaz et al., Electrochimica Acta [Chinese Journal of Electrochemistry](2014), 133, 501-508). Similarly, aromatic polyamide nanofibers have been used as separator membrane materials (B. Yang, J. Mat. Chem. A: Mat. Energy Sustain. [Journal of Materials Chemistry A: Energy and Sustainable Materials](2021), 9(22) 12923-12946). Polyamides have been used as a carbon source for conductive carbon coatings on vanadate-based active materials (J. Yan et al., RSCA Advances [RSC Progress] (2016), 6(114), 113228-113228). Polyamides have been further used as one of the layers on the metal foil of battery packaging in JP 2011175841. From this, it can be indirectly inferred that polyamides may have sufficient electrochemical stability. However, there is no indication of the use of polyamides or other condensation polymers in the sense of this invention.

[0028] JP 2015005391 A describes polyamic acids that exist partly as salts and are soluble in NMP, serving as adhesives. However, these polymers may be too reactive with highly alkaline active materials.

[0029] In JP 2007305574 A, an aromatic p-amide soluble in NMP was prepared; however, the high modulus of this resin may lead to a lack of electrode flexibility.

[0030] The composite material according to the invention allows for the provision of an advantageous HNBR binder to deliver a high-solids-content cathode slurry with low viscosity. More specifically, the invention can modify HNBR to achieve even higher solids content and thus greater energy savings in the cathode manufacturing process by preparing a composite material. It is believed that such a composite material can potentially provide bonding characteristics that are still lacking when HNBR is used solely as a binder.

[0031] HNBR is a flexible, rubber-like material that, compared to PVDF, allows for the production of a softer and more flexible cathode film under similar forces. According to the invention, the modulus of the HNBR-based adhesive can be further adjusted, for example, making the adhesive polymer harder. Thin cathodes can allow for a harder polymer adhesive, while thicker cathodes may require a softer adhesive. Therefore, very high fit becomes possible.

[0032] Binder composites allow for even higher solids content, which provides good adhesion to the current collector and good bonding strength within the electrode. Gelation problems are suppressed or at least reduced. In terms of dosage, binder composites can allow the same or even higher efficiency at lower dosages compared to PVDF.

[0033] Adding domains formed from condensates selected from polyamides and polyesters as defined above allows them to act as dispersants, binders, or rheology modifiers in battery adhesives.

[0034] According to the present invention, it is further shown that providing a domain formed from the corresponding condensation polymer does not require the addition of a fluorinated binder polymer. Therefore, a significant advantage of the present invention is that the use of fluorinated binders can be avoided.

[0035] This invention provides a method for combining HNBR with a suitable thermoplastic resin (i.e., polyamide or polyester) to create a novel adhesive system. This resin can be selected to provide an adhesive film with a higher modulus while maintaining its flexibility. This resin further allows for improved adhesive adhesion properties.

[0036] Another aspect of battery technology is becoming increasingly urgent: the recycling of spent batteries. Several technologies have been proposed, such as pyrolysis or hydrometallurgical methods, to separate current collectors from active materials and recycle them in some way by extracting valuable raw materials to manufacture new batteries. However, the low content of polymers used as binders or modifiers complicates these processes. In particular, the presence of organically bound fluorine polymers according to existing technologies poses a significant challenge because removal requires pyrolysis of battery materials at high temperatures. Fluorinated polymers will be decomposed to form HF. This gas needs to be washed away from the exhaust gas, and HF is highly corrosive and limits the lifespan of equipment. However, the binder composites of the present invention, which are free of fluorine or even halogenated compounds, are easier to remove during battery recycling and have therefore found great technological appeal in addressing these problems.

[0037] Therefore, the adhesive composite material according to the invention also facilitates battery recycling because the decomposition of organofluorine materials is not required when recovering valuable metals, metal oxides and carbon materials.

[0038] Generally, as is known in the art, hydrogenated nitrile butadiene rubber (NBR) is a copolymer formed from acrylonitrile and 1,3-butadiene, wherein the double bonds of the NBR units are at least largely hydrogenated. In a preferred embodiment, the hydrogenated NBR contains acrylate units, wherein the sum of the remaining hydrocarbon-based monomer units is less than 70 wt.-%. In other words, the amount of acrylate units is in the range of at least 30 wt.-%, such as in the range of 30 to 50 wt.-%. This embodiment allows for the customization of adhesive composite properties (such as elasticity) to be particularly well suited for electrode adhesives.

[0039] Furthermore, regarding the degree of hydrogenation of HNBR, it is preferable that the degree of hydrogenation, as measured by RDB, is less than 1%.

[0040] In particular, hydrogenated nitrile rubber is preferred to have a nitrile content of 7 to 55 wt.-% (preferably 15 to 40 wt.-%) calculated as acrylonitrile and a degree of hydrogenation of less than 1% as measured by RDB.

[0041] Preferred hydrogenated nitrile butadiene rubber may further contain 0 to 30 wt.% of polymeric monomer units selected from acrylates or methacrylates.

[0042] According to another preferred embodiment, the content of the condensation polymer is in the range of 5 to 40 phr, where 100 phr refers to hydrogenated nitrile butadiene rubber. It has been shown that the advantages of the invention are particularly effective when the polyamide is present in the amount defined in such embodiments.

[0043] Furthermore, preferably, the binder composite material is present in the electrode coating dispersion, which contains an electrochemically active material and a conductive carbon material dispersed in an organic solvent. According to this embodiment, in addition to the binder composite material, the active material and the conductive material are also present in a solvent such as NMP. This allows the binder composite material to be applied as a dispersion in a very simple manner. For example, the binder composite material or the binder dispersion can be applied to the current collector separately.

[0044] In another preferred embodiment, the binder composite material is present in an electrode coating dispersion containing a solid electrolyte dispersed in an organic solvent, optionally an electrochemically active material, and optionally a conductive carbon material. Therefore, the binder composite material can also be used, and preferably, in a dispersion having a solid electrolyte.

[0045] It was found that it was not possible to produce the corresponding composites by combining these different polymers in a solution simply by combining HNBR with the defined polyamide or polyester. The solution blending step resulted in phase separation of the polymers within the solution, making the binder solution unusable. Therefore, it was necessary to find a way to combine HNBR and resin in a manner that allowed for the production of a stable solution for the binder system.

[0046] Therefore, it has been found that the described condensation polymers are generally insoluble in process solvents, primarily N-methylpyrrolidone (NMP). Consequently, the condensation polymer resins cannot be used directly in wet coating processes for cathodes.

[0047] However, it has been shown that the domain of condensation polymer formation within the HNBR matrix can be achieved particularly effectively using a melt-mixing process. In detail and surprisingly, the melt-mixing process of HNBR and condensation polymers has proven suitable for producing soluble binder composites. Melt mixing can be performed in any apparatus that allows for controlled application of shear and temperature to the mixture. Twin-screw extruders or planetary extruders are very suitable and commonly used machines for melt-mixing processes. However, the type of melt mixer can be varied where the temperature can be well controlled along the process time and length, and where shear can be applied mechanically for a limited time. Suitable melt-mixing machines can also be planetary roll extruders, oscillating single-spindle extruders, such as the oscillating single-spindle extruders available as kneaders from Buss. However, it is believed that excessively high temperatures or excessively long mixing times can damage the HNBR matrix.

[0048] Melt mixing refers to the melting behavior in which condensation polymers are mixed when they reach or exceed their melting temperature to a certain extent. In the case of amorphous condensation polymers (i.e., polyamides or polyesters), melt mixing must be carried out sufficiently above the glass transition temperature so that the melt viscosity is low enough to allow for good dispersion in the HNBR matrix.

[0049] The melt blending of HNBR with, for example, polyamide has been described in US 2020392316 A1 and WO 2019121157A1; however, these disclosures do not mention any possible uses as a dispersant, binder, or rheology modifier in batteries. No disclosure is made of melt-blended HNBR / condensate composites for use in batteries.

[0050] Melt mixing is understood as the process of transitioning the resin to a molten stage during mixing to allow it to disperse into the rubber matrix. This means reaching a melt temperature is necessary. The melt temperature of the resin can be determined using common analytical methods such as DSC scanning. Further optimization can be performed by examining the viscosity of the molten resin and HNBR at a given temperature. A viscosity ratio of HNBR rubber to resin between 1.3 and 5 is generally favorable for resin dispersion in the rubber (see M. Hemstede, J. Dodevski, A. Kaiser, S. Lieber, 13). th Fall RubberColloquium [13th Autumn Rubber Conference], November 7, 2018.

[0051] Therefore, it is preferable that the viscosity ratio of HNBR to condensate is between 1.3 and 5.

[0052] For further technical features and advantages of composite materials, refer to the description of electrodes, electrochemical energy storage devices, examples and figures.

[0053] An electrode for an electrochemical energy storage device is further described, wherein the electrode comprises a binder composite material configured as described above.

[0054] For example, an adhesive composite material can be applied to the current collector of the electrode (such as aluminum foil). In particular, the electrode can form a cathode.

[0055] Providing a binder composite material in the electrode (such as the cathode) particularly offers the advantages described above for binder composite materials.

[0056] Another advantage is the strong bonding of the cathode material to the current collector, which is typically a thin aluminum foil. Insufficient bonding can lead to cathode peeling when the cathode is bent within the core of a cylindrical cell. This can result in loss of electrical contact, causing battery failure. Another problem is the uneven electrode edges caused by material loss during slitting or cutting to size. This can even lead to a short circuit between the cathode and anode current collectors.

[0057] In another aspect of the invention, a very thin coating of carbon material is used to equip the current collector foil with a conductive layer before applying the electrode paste. This thin coating can be based on carbon black, carbon nanotubes, or graphene, and requires an adhesive to properly bond it to the metal current collector. The polymeric adhesive can advantageously be an HNBR composite material (due to its adhesion and strength).

[0058] It has been shown that the defined condensation domains in the HNBR can facilitate the dispersion of conductive carbon materials in organic solvents. Therefore, the binder composite material is particularly preferred for forming dispersions as described.

[0059] Accordingly, the defined condensation domains in HNBR can help disperse solid electrolytes in organic solvents and, optionally, other additives intended for use in solid-state batteries.

[0060] For further technical features and advantages of the electrodes, refer to the description of composite materials, electrochemical energy storage devices, examples and figures.

[0061] An electrochemical energy storage device is further described, wherein the electrochemical energy storage device includes an anode and a cathode, the cathode being configured as previously described.

[0062] Specifically, the electrochemical energy storage device is a secondary battery, such as a lithium-ion battery. It includes an anode, a cathode, and a separator located between the anode and the cathode in a manner known per se. The anode may be formed of graphite or other materials known in the art, and the separator may include polymer foil or ceramic structures as known to those skilled in the art.

[0063] The cathode is configured as described above, which allows for the corresponding advantages as stated above.

[0064] For further technical features and advantages of electrochemical energy storage devices, refer to the description of composite materials, electrodes, examples and figures.

[0065] Composite materials are described in more detail below.

[0066] HNBR

[0067] First, it is important to clarify the main adhesive, HNBR. In the context of this application, "nitrile-diene copolymer" (nitrile-butadiene copolymer, nitrile rubber, also abbreviated as "NBR") is understood to mean a copolymer, trimer, or tetramer of at least one α,β-encapsulated unsaturated nitrile, at least one conjugated diene, and optionally one or more additional copolymerizable monomers. Therefore, the term also covers copolymers having two or more α,β-encapsulated unsaturated nitrile monomer units and two or more conjugated diene monomer units.

[0068] "Hydrogenated nitrile-diene copolymer" ("HNBR") should be understood to mean a copolymer, trimer, or tetramer in which at least some, preferably at least 50%, of the C=C double bonds in the copolymerized diene units have been hydrogenated. For sufficient electrochemical stability, it is preferred that the hydrogenated HNBR rubber is fully hydrogenated.

[0069] The term "fully hydrogenated" means that the degree of hydrogenation of the butadiene units in the hydrogenated nitrile-diene copolymer is 99.1% to 100%.

[0070] The term "copolymer" covers polymers having more than one monomer unit.

[0071] α,β-olefinic unsaturated nitrile

[0072] The α,β-olefinically unsaturated nitrile used (which forms α,β-olefinically unsaturated nitrile units) can be any known α,β-olefinically unsaturated nitrile. Preferred are (C3-C5)-α,β-olefinically unsaturated nitriles (such as acrylonitrile), α-haloacrylonitriles (e.g., α-chloroacrylonitrile and α-bromoacrylonitrile), α-alkylacrylonitriles (e.g., methacrylonitrile, ethylacrylonitrile), or mixtures of two or more α,β-olefinically unsaturated nitriles. Particularly preferred are acrylonitrile, methacrylonitrile, ethylacrylonitrile, or mixtures thereof. Acrylonitrile is very particularly preferred.

[0073] The amount of α,β-olefinic unsaturated nitrile units is typically in the range of 10% to 60% by weight, preferably 15% to 50% by weight, and more preferably 17% to 44% by weight, of the total amount of all monomer units in HNBR-based rubber, representing 100% of the total amount.

[0074] Conjugated dienes

[0075] The conjugated diene forming the conjugated diene unit can be any conjugated diene, especially conjugated C4-C12 dienes. Preferred are 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene (pentadiene), 2-chloro-1,3-butadiene, or mixtures thereof. Particularly preferred are 1,3-butadiene and isoprene, or mixtures thereof. 1,3-butadiene is particularly preferred.

[0076] The amount of conjugated diene is typically in the range of 40% to 90% by weight, preferably 50% to 85% by weight, and more preferably 56% to 83% by weight, of the total amount of all monomer units in the HNBR-based rubber, representing 100% of the total amount.

[0077] Other comonomers

[0078] α,β-olefinic unsaturated carboxylic acid ester units

[0079] In addition to α,β-olefinic unsaturated nitrile units and conjugated diene units, HNBR rubber may also contain at least one α,β-olefinic unsaturated carboxylic acid ester unit.

[0080] A typical α,β-olefinic unsaturated carboxylic acid ester unit is:

[0081] o Alkyl methacrylates, especially C4-C18 alkyl methacrylates, preferably n-butyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate or n-hexyl methacrylate;

[0082] o Alkoxyalkyl esters of (meth)acrylate, especially C4-C18-alkoxyalkyl esters of (meth)acrylate, preferably C4-C12-alkoxyalkyl esters of (meth)acrylate;

[0083] o (meth)acrylate hydroxyalkyl esters, especially (meth)acrylate C4-C18-hydroxyalkyl esters, preferably (meth)acrylate C4-C12-hydroxyalkyl esters;

[0084] o (meth)acrylate cycloalkyl esters, especially (meth)acrylate C5-C18-cycloalkyl esters, preferably (meth)acrylate C6-C12-cycloalkyl esters, more preferably (meth)acrylate cyclopentyl ester, (meth)acrylate cyclohexyl ester, (meth)acrylate cycloheptyl ester;

[0085] o Alkylcycloalkyl esters of (meth)acrylate, especially C6-C12-alkylcycloalkyl esters of (meth)acrylate, preferably C7-C10-alkylcycloalkyl esters of (meth)acrylate, more preferably methylcyclopentyl esters of (meth)acrylate and ethylcyclohexyl esters of (meth)acrylate;

[0086] o Aryl monoesters, especially C6-C14-aryl monoesters, preferably phenyl (meth)acrylate or benzyl (meth)acrylate;

[0087] o Amino-containing α,β-ene unsaturated carboxylic acid esters, such as dimethylaminomethyl acrylate or diethylaminoethyl acrylate;

[0088] o α,β-olefinic unsaturated dicarboxylic acid monoalkyl esters, preferably

[0089] Alkyl monoesters, especially C4-C18-alkyl monoesters, preferably n-butyl, tert-butyl, n-pentyl, or n-hexyl monoesters, more preferably n-butyl maleate, n-butyl fumarate, n-butyl citracate, or n-butyl itaconic acid, and most preferably n-butyl maleate.

[0090] Alkoxyalkyl monoesters, especially C4-C18-alkoxyalkyl monoesters, preferably C4-C12-alkoxyalkyl monoesters,

[0091] Hydroxyalkyl monoesters, especially C4-C18-hydroxyalkyl monoesters, preferably C4-C12-hydroxyalkyl monoesters,

[0092] Cycloalkyl monoesters, especially C5-C18-cycloalkyl monoesters, preferably C6-C12-cycloalkyl monoesters, and more preferably monocyclopentyl maleate, monocyclohexyl maleate, monocycloheptanyl maleate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclopentyl citrate, monocyclohexyl citrate, monocycloheptanyl citrate, monocyclopentyl itaconic acid, monocyclohexyl itaconic acid, and monocycloheptanyl itaconic acid.

[0093] Alkylcycloalkyl monoesters, especially C6-C12-alkylcycloalkyl monoesters, preferably C7-C10-alkylcycloalkyl monoesters, more preferably monomethylcyclopentyl maleate and monoethylcyclohexyl maleate, monomethylcyclopentyl fumarate and monoethylcyclohexyl fumarate, monomethylcyclopentyl citrate and monoethylcyclohexyl citrate, monomethylcyclopentyl itaconic acid and monoethylcyclohexyl itaconic acid.

[0094] Aryl monoesters, especially 06-014-aryl monoesters, preferably monoaryl maleate, monoaryl fumarate, monoaryl citrate, or monoaryl itaconic acid, particularly preferably monophenyl maleate or monobenzyl maleate, monophenyl fumarate or monobenzyl fumarate, monophenyl citrate or monobenzyl citrate, monophenyl itaconic acid or monobenzyl itaconic acid.

[0095] Unsaturated polyalkyl polycarboxylic acid esters, such as dimethyl maleate, dimethyl fumarate, dimethyl itaconic acid, or diethyl itaconic acid;

[0096] Or a mixture thereof.

[0097] In a particularly preferred embodiment, the fully or partially hydrogenated HNBR rubber contains (O1-O4)-alkyl methacrylate, most preferably butyl acrylate.

[0098] The amount of optional α,β-olefinic unsaturated carboxylic acid ester units in the HNBR rubber according to the invention is typically in the range of 0% to 30% by weight, preferably 0.5% to 20% by weight, and more preferably 1% to 10% by weight, based on 100% of the total amount of all monomer units.

[0099] The manufacture of this type of rubber is well known in industry and is described, for example, in the Handbook of Synthetic Rubber (general description of rubber is on pages 67-86 of Chapter 5, and specifically on pages 295-314 of Chapter 14 for HNBR), ARLANXEO Deutschland GmbH, Germany, 2020.

[0100] Monomers used in polymerization are typically obtained from fossil sources, such as through crude oil cracking, but monomers from sustainable sources can also be used. Using monomers from sustainable sources has the advantage of reducing the carbon dioxide footprint of the polymer and the products made from them. Monomers from sustainable sources include those derived from biological sources, including plants, fungi, or bacteria. These monomers are chemically identical to those from fossil sources but have a higher carbon-14 isotope content, by which they can be identified. Monomers from sustainable sources also include those derived from recycled waste, including recycled biological waste (e.g., wood pulp), recycled rubber waste (e.g., from the pyrolysis of tires), and recycled plastic waste. Monomers derived from recycled materials also include ISCC+ certified monomers, which can be used, for example, in so-called mass balance methods to reduce the total CO2 content of the production chain (see, for example, Pete Spanos et al., “Sustainable Keltan EPDM”, RUBBERWORLD.COM, April 2023, which describes methods for EPDM polymers, but the principles illustrated therein can also be applied accordingly to other polymers). Monomers from sustainable sources may have to, or may not necessarily have to, be purified differently from those derived from fossil sources to provide monomers of the same purity.

[0101] polyamide

[0102] The polyamide in the adhesive composite material according to the invention is a combination of diamine and dicarboxylic acid, prepared from ω-aminocarboxylic acid or the corresponding lactam. In principle, any aliphatic polyamide can be used, preferably PA6, PA66, PA610, PA88, PA612, PA810, PA108, PA9, PA613, PA614, PA812, PA1010, PA10, PA814, PA148, PA1012, PA11, PA1014, PA1212, or PA12. However, polyamide 6 may be particularly preferred in terms of the advantages achieved.

[0103] Nylon-6 (PA6) or Nylon-6,6 (PA66) is preferred, and Nylon-6 is particularly preferred.

[0104] The preferred polyamides according to the present invention are semi-crystalline or amorphous polyamides that can be prepared from diamines and dicarboxylic acids and / or lactams or corresponding amino acids having at least 5 ring members.

[0105] Useful reactants are preferably aliphatic and / or aromatic dicarboxylic acids, more preferably adipic acid, 2,2,4-trimethyladipic acid, 2,4,4-trimethyladipic acid, azelaic acid, sebacic acid, isophthalic acid, and terephthalic acid; aliphatic and / or aromatic diamines, more preferably tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, nonane-1,9-diamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine, isomers of diaminodicyclohexylmethane, diaminodicyclohexylpropane, bis(aminomethyl)cyclohexane, phenylenediamine, and diphenylenediamine; aminocarboxylic acids, especially aminohexanoic acid, or the corresponding lactams. Copolyamides including the various monomers mentioned above are also included.

[0106] Suitable polyamides according to the invention are known, for example, under the trademarks Durethan® or Nylon®. Most preferably, Durethan® B31F PA 6 from LANXESS is used. Of course, mixtures of these polyamides can also be used, wherein the mixing ratio is as desired. A certain proportion of recycled polyamide molding materials and / or fiber recycling may also be present.

[0107] The polyamide preferably has a relative viscosity of 2.3 to 4.0, more preferably 2.7 to 3.5, wherein the relative viscosity can be determined / measured at 25°C on a 1% by weight solution of m-cresol.

[0108] The preparation of polyamides is a prior art. Of course, copolyamides based on the above-mentioned polyamides can be used as an alternative.

[0109] Many procedures for preparing polyamides have become known, in which different monomer units and various chain transfer agents are used to establish the desired molecular weight, or alternatively, monomers with reactive groups are used, depending on the desired end product. Industrially relevant methods for preparing polyamides for use in mixtures of substances are preferably carried out via polycondensation in a melt. In this context, the hydrolytic polymerization of lactams is also considered polycondensation. The preparation of polyamides by thermal polycondensation is known to those skilled in the art; see in particular Nylon Plastics Handbook, Hanser-Verlag, Munich, 1995, pp. 17-27 and Kunststoff-Handbuch Plastics Handbook 3 / 4, Polyamide, Carl Hanser-Verlag, Munich, 1998, pp. 22-36.

[0110] Particularly preferred are random, semi-crystalline, aliphatic PA 6 / 66 copolyamides polymerized from ε-caprolactam and hexamethylenediamine adipic acid salt.

[0111] ε-caprolactam (CAS No. 105-60-2) is particularly preferred for preparing polyamides. Cyclohexanone oxime is first prepared from cyclohexanone by reacting with the hydrogen sulfate or hydrochloride salt of hydroxylamine. This cyclohexanone oxime is then converted to ε-caprolactam via the Beckmann rearrangement.

[0112] Hexamethylenediamine adipic acid salt (CAS No. 3323-53-3) is the reaction product of adipic acid and hexamethylenediamine. One of its uses is as an intermediate in the preparation of nylon-6,6. Its common name, AH salt, comes from the first letter of the starting material.

[0113] Mixtures of different polyamides can also be used, provided they are sufficiently compatible. Compatible combinations of polyamides are known to those skilled in the art. Preferred polyamide combinations are PA6 / PA66, PA12 / PA1012, PA12 / 1212, PA612 / PA12, PA613 / PA12, PA1014 / PA12, or PA610 / PA12, and corresponding combinations with PA11, with PA6 / PA66 being more preferred. In case of doubt, the compatible combination can be determined by routine experiments.

[0114] Instead of aliphatic polyamides, semi-aromatic polyamides can advantageously be used, wherein the dicarboxylic acid component is derived from an aromatic dicarboxylic acid having 8 to 22 carbon atoms in the range of 5 to 100 mol%, and the semi-aromatic polyamide preferably has a microcrystalline melting point Tm of at least 250°C, more preferably at least 260°C, and particularly preferably at least 270°C according to ISO 11357-3. This type of polyamide is typically identified by the addition of T (=semi-aromatic). They can be prepared from combinations of diamines and dicarboxylic acids, optionally with the addition of ω-aminocarboxylic acids or corresponding lactams. Suitable types are preferably PA66 / 6T, PA6 / 6T, PA6T / MPMDT (MPMD stands for 2-methylpentamethylenediamine), PA9T, PA10T, PA11T, PA12T, PA14T, and cocondensates of these latter types with aliphatic diamines and aliphatic dicarboxylic acids or with ω-aminocarboxylic acids or lactams. Semi-aromatic polyamides can also be used in the form of blends with another polyamide, preferably an aliphatic polyamide, more preferably PA6, PA66, PA11 or PA12.

[0115] Another suitable category of polyamides is the transparent polyamide category; these are mostly amorphous, but can also be microcrystalline. They can be used alone or in mixtures with aliphatic and / or semi-aromatic polyamides, preferably PA6, PA66, PA11, or PA12. The glass transition point Tg, measured according to ISO 11357-3, is at least 110°C, preferably at least 120°C, more preferably at least 130°C, and even more preferably at least 140°C. Preferred transparent polyamides are polyamides of dodecane-1,12-diacid and 4,4′-diaminodicyclohexylmethane (PAPACM12) (especially starting from 4,4′-diaminodicyclohexylmethane having a trans-trans isomer content of 35% to 65%), polyamides of terephthalic acid and / or isophthalic acid and isomers of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, polyamides of isophthalic acid and hexamethylene-1,6-diamine, mixtures of terephthalic acid / isophthalic acid, and hexamethylenediamine. A copolyamide of methylene-1,6-diamine (optionally a mixture with 4,4′-diaminodicyclohexylmethane), a copolyamide of terephthalic acid and / or isophthalic acid, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and laurolactam or caprolactam, a (co)polyamide of dodecane-1,12-diacid or sebacic acid, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and optionally laurolactam or caprolactam, isophthalic acid, 4,4′-diaminodicyclohexylmethane and laurolactam or caprolactam. Copolyamides of laurolactam or caprolactam, polyamides of dodecane-1,12-diacid and 4,4′-diaminodicyclohexylmethane (with low trans-trans isomer content), copolyamides of terephthalic acid and / or isophthalic acid and alkyl-substituted bis(4-aminocyclohexyl)methane homologues (optionally in mixtures with hexamethylenediamine), copolyamides of bis(4-amino-3-methyl-5-ethylcyclohexyl)methane (optionally with additional diamines) and isophthalic acid (optionally with additional dicarboxylic acids), and so on. Copolyamides of mixtures of phenylenediamine and other diamines (e.g., hexamethylenediamine) and isophthalic acid (optionally with other dicarboxylic acids such as terephthalic acid and / or naphthal-2,6-dicarboxylic acid), copolyamides of mixtures of bis(4-aminocyclohexyl)methane and bis-(4-amino-3-methyl-cyclohexyl)methane and copolyamides of aliphatic dicarboxylic acids having 8 to 14 carbon atoms, and polyamides or copolyamides formed from mixtures containing tetradecane-1,14-diacid and aromatic, arylexicon or alicyclic diamines.

[0116] These examples can be significantly varied by adding additional components, preferably caprolactam, laurolactam, or diamine / dicarboxylic acid combinations, or by partially or completely replacing the starting components with other components.

[0117] The lactam or ω-aminocarboxylic acid used as the monomer to form the polyamide contains 4 to 19, and especially 6 to 12, carbon atoms. Particularly preferred are ε-caprolactam, ε-aminohexanoic acid, octanolactam, ω-aminooctanoic acid, laurolactam, ω-aminododecanoic acid, and / or ω-aminoundecanoic acid.

[0118] Combinations of diamines and dicarboxylic acids include, for example, hexamethylenediamine / adipic acid, hexamethylenediamine / dodecanoic acid, octamethylenediamine / decanedioic acid, decanediamine / decanedioic acid, decanediamine / dodecanoic acid, dodecylmethylenediamine / dodecanoic acid, and dodecylmethylenediamine / naphthalene-2,6-dicarboxylic acid. Furthermore, all other combinations can be used alternatively, particularly decamethylenediamine / dodecanoic acid / terephthalic acid, hexamethylenediamine / adipic acid / terephthalic acid, hexamethylenediamine / adipic acid / caprolactam, decamethylenediamine / dodecanoic acid / ω-aminoundecanoic acid, decamethylenediamine / dodecanoic acid / laurolactam, decamethylenediamine / terephthalic acid / laurolactam, or dodecylmethylenediamine / naphthalene-2,6-dicarboxylic acid / laurolactam.

[0119] Many linear aliphatic polyamides can be classified according to their melting points. Since the composites of the present invention are prepared by melt blending, the melting point of the condensation polymer determines the processing temperature. For example, PA6 has a melting point in the range of approximately 225°C. Therefore, a suitable processing temperature is about 230°C. In the case of PA66, the melting point is about 270°C, making melt processing should be carried out at or slightly above this temperature. This is considered close to the upper limit of the acceptable processing temperature for HNBR components, making PA66 a less preferred resin for the composites of the present invention.

[0120] A simple guideline for selecting a suitable polyamide is the amide frequency, which is 100 times the number of amide linkages divided by the total number of atoms along the chain (see K. Marchildon, Macromol. React. Eng [Macromolecular Reaction Engineering]. 2011, 5, 22-54). A high amide frequency will give a higher melting point. PA66 is an AABB type polyamide with an amide frequency of 14.3. Therefore, in the case of linear aliphatic AABB polyamides, the amide frequency should not exceed 15, and an amide frequency of 13 is more preferred.

[0121] Linear aliphatic AB polyamides provide suitable processing temperatures for producing the composites of the present invention. PA6 has an amide frequency of 14.3, PA11 has an amide frequency of 8.3 and a melting point of 183°C, and PA12 has an amide frequency of 7.7 and a melting point of 180°C. AB polyamides can also be used as terpolymers (called terpo) with melting points in the range of 150°C to 190°C, and are therefore considered very suitable.

[0122] Aromatic polyamides can be used; however, these polyamides tend to have considerably higher melting points than PA66. Some structural variants of aromatic or semi-aromatic polyamides with lower melting temperatures exist, and these variants can then be used as components in composite materials.

[0123] The amount of polyamide in the composite material according to the invention is 5 wt.-% and up to 50 wt.-%. However, the polyamide content should not exceed the amount in the composite material where HNBR is no longer a continuous phase. It is quite preferred that the island morphology be achieved by polyamide forming islands within a continuous HNBR matrix. If the amount of polyamide is too small (i.e., less than 5%), the improvement in adhesion and viscosity reduction is no longer sufficiently strong.

[0124] If the amount of polyamide is too high, the polyamide may form a continuous phase, and the composite material may be incompletely or too difficult to dissolve in organic solvents such as NMP, and may require excessively high dissolution temperatures.

[0125] With precise amounts of polyamide, this resin will form small domains in the HNBR range of several hundred nanometers or several micrometers. During dissolution in NMP, the HNBR phase will dissolve readily, while the polyamide will form small, partially swollen particles that form a stable dispersion within the HNBR solution.

[0126] Surprisingly, the obtained polyamide suspension in HNBR in NMP solution was stable. Unbound by theory, it is believed that HNBR can interact to some extent with the PA particles to act as a stabilizing layer. Otherwise, it is well known that binary blends of polymers in solution will eventually separate unless they have a sufficiently high negative enthalpy of mixing.

[0127] Polyester

[0128] The polyester can be selected from thermoplastic polyesters and thermoplastic polyester elastomers and blends thereof. Preferred thermoplastic polyesters are polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), and should contain at least 90 mol% terephthalic acid units based on the dicarboxylic acid unit content. They should contain diol components, which are preferably ethylene glycol units or butanediol units. Thus, thermoplastic polyesters are primarily esters of aromatic diacids.

[0129] Examples of aromatic dicarboxylic acids or their derivatives include dimethyl terephthalate, dimethyl isophthalate, terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid. Examples of aliphatic diols include butanediol and hexanediol.

[0130] In addition to the terephthalic acid portion, preferred polyethylene terephthalate and polybutylene terephthalate may also contain up to 20 mol% of other aromatic dicarboxylic acids having 8 to 14 carbon atoms, or aliphatic dicarboxylic acids having 4 to 12 carbon atoms, such as phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4′-diphenyldicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, or portions of cyclohexane-dicarboxylic acid and cyclohexane-diacetic acid.

[0131] In addition to the ethylene glycol and 1,4-butanediol portions, preferred polyethylene terephthalate and polyethylene terephthalate may each contain up to 20 mol% of other aliphatic diols having 3 to 12 carbon atoms or alicyclic diols having 6 to 21 carbon atoms, preferably portions of 1,3-propanediol, 2-ethyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3- or -1,6-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 2,5-hexanediol, and 1,4-cyclohexane-diethanol.

[0132] Thermoplastic polyester elastomers comprise thermoplastic polyesters as described above, wherein poly(epoxy)polymer segments derived from the corresponding poly(epoxy)diols are added. These segments preferably have a molecular weight of 500 to 3,000 Da to provide a flexible elastic chain component within the thermoplastic elastomer. The elastic segments are commonly referred to as soft blocks.

[0133] The preferred diol component is either poly(butanediol) diol or poly(ethylene glycol) diol, which can also be used in combination. The amount of endopeptide (epoxy) in the thermoplastic elastomer is in the range of 10 to 45 mol% of diol units based on the diol fraction of the thermoplastic polyester segment. General properties and synthesis of thermoplastic elastomers can be found in Z. Roslaniec (Chapter 3 Polyester Thermoplastic Elastomers: Synthesis, properties, and some Applications), Wiley-VCH Handbook of Condensation Thermoplastic Elastomers, Weinheim ISBN 3-527-30976-4.

[0134] solvent

[0135] Organic solvents allow for the dissolution of binders or binder composites as a necessary step in producing the electrode slurry for coating. This further allows for the dispersion of conductive materials such as carbon nanotubes. In this case, the binder composite acts as a dispersing aid. Typical solvents are NMP, DMF, valproic acid lactone, butyrolactone, xylene and other aromatic compounds, various esters and ethers, and ether esters. Low-polarity solvents are primarily used in solid-state batteries, where the process solvent needs to be compatible with the solid electrolyte.

[0136] The process solvent must be selected to allow for the dissolution of HNBR, and the solubility of a particular HNBR grade depends on its structure. However, the resin, as part of the binder composite material, does not need to be soluble in the process solvent at all. In fact, the advantage of the composite material of the present invention is that insoluble resins can be introduced into the wet electrode manufacturing process, and therefore a greater selection of resins is possible regardless of their solubility in the solvent.

[0137] The composite materials of the present invention based on HNBR and condensation resins (i.e., polyamides or polyesters as described) can be used in the coating process of LiB cathodes and in SSBs because stable, fine-grained dispersions can be obtained in polymer solutions. These solutions can be used as binders, rheology modifiers, and polymer dispersion aids for conductive carbon pastes (e.g., for preparing carbon nanotube pastes).

[0138] The Molau test is a specialized method for testing the stability of composite material solutions in battery process solvents. The Molau test is performed by dissolving the composite material in a solvent known to form a continuous matrix but not a dispersed polymer. If the dispersed polymer separates into an upper or lower layer according to density, the composite material is considered incompatible. If a turbid, stable solution is obtained, the dispersed phase is compatibilized. Conventionally, a third polymer is required as a compatibilizer, such as the one described by Huahao Yang et al. (Yang, H., Cao, X., Ma, Y., An, J., Ke, Y., Liu, X., and Wang, F. (2011). Effect of maleic anhydride grafted polybutadiene on the compatibility of polyamide 66 / acrylonitrile-butadiene-styrene copolymer blend. Polymer Engineering & Science, 52(3), 481–488), to disperse ABS in PA66.

[0139] Similarly, when maleic anhydride-grafted EPDM is used as a compatibilizer, only stable, opaque solutions of PA6 with dispersed EPDM can be obtained, see Xu et al. (M. Xu, W. Qiu, G. Qiu., Journal of Macromolecular Science, Part B: Physics, 52, 155-166, 2013). The authors used the term Molau test to characterize stable solutions of compatibilized polymer blends. GE Molau described stable solutions of immiscible polymers based on emulsification in the mid-1960s and early 1970s, as in GE Molau, J. Polym. Sci., Part A, General papers (1965), 3(4) 1267-1278.

[0140] [Ethylene-propylene elastomer grafted maleic anhydride toughened polyamide-6 morphology and properties], J. Macromol. Science, Part B Physics, 52:155-166, 2013. Furthermore, LDPE needs to be grafted with glycidyl methacrylate to allow for melt blending with PA-6 and then passing the Molau test (Q. Wei et al., Functionalization of LDPE by meltgrafting with glycidyl methacrylate and reactive blending with polyamide-6), Macromol. Chem. Phys. (2003) 204(8), 1123-1133.

[0141] Surprisingly, high compatibility was achieved in the melt-mixed HNBR and defined condensate composite of the present invention without the use of any third polymer as a compatibilizer. The two polymers are considered immiscible. No grafting reaction is performed, and melt mixing is carried out, thus avoiding excessively high temperatures or long mixing times.

[0142] Surprisingly, the Molau test, which was developed solely to assess polymer compatibility, can now be used to design soluble composite materials in liquid form for use as binders, rheology modifiers, and dispersants in lithium-ion batteries.

[0143] To date, the Molau test has not been applied to composites based on a combination of nitrile rubber or HNBR with condensation polymers as defined (i.e., polyamides or polyesters).

[0144] Example

[0145] Materials used:

[0146] HNBR 1: 34% nitrile content (ISO 24698-1), Mooney viscosity of 63 MU (Ml1+4, 100°C) according to ISO 289 / ASTM D 1646, and unsaturation of < 0.9% based on residual double bond content (RDB, IR spectroscopy), wherein the parent NBR will have 100% RDB.

[0147] HNBR 2: 34% nitrile content (ISO 24698-1), Mooney viscosity of 70 MU (Ml1+4, 100°C) according to ISO 289 / ASTM D 1646, and unsaturation of < 0.9% based on residual double bond content (RDB, IR spectroscopy).

[0148] HNBR 3: 17% nitrile content (ISO 24698-1), Mooney viscosity of 70 MU (Ml1+4, 100°C) according to ISO 289 / ASTM D 1646, and unsaturation of <0.9% based on residual double bond content (RDB, IR spectroscopy). This polymer contains acrylate monomer units and is amorphous (DSC temperature scan, Tg -43°C). Hydrocarbon-based monomer units are less than 65%.

[0149] HNBR 4: 34% nitrile content (ISO 24698-1), Mooney viscosity of 40 MU (Ml1+4, 100°C) according to ISO 289 / ASTM D 1646, and unsaturation of < 0.9% based on residual double bond content (RDB, IR spectroscopy).

[0150] HNBR 5: An HNBR with a nitrile content of 27% (ISO 24698-1), <0.9% unsaturation (RDB, IR spectroscopy), and a Mooney viscosity of 70 MU (Ml1+4, 100°C) according to ISO 289 / ASTM D 1646, prepared by hydrogenation of nitrile butadiene rubber with a nitrile content of 28% and a Mooney viscosity of 45 MU (Ml1+4, 100°C). The content of hydrocarbon-based monomer units is 73%.

[0151] PA6, Durethan® B31F: Unreinforced, extrusion-grade, low-viscosity, additive-free PA 6 with a melting point of 222°C (ISO 11357-1, -3 222), supplied by Lanxess AG.

[0152] Terpo PAZN150 from Yixing Chemical Reagent Factory, China: melting point 150°C, derived from a copolymer of PA6, PA66, and PA1010 in a weight ratio of 10% / 20% / 70%. The amide frequency is calculated to be 10.7.

[0153] Terpo PA ZN 170 from Yixing Chemical Reagent Factory, China: melting point 165°C, a copolymer of PA6, PA66 and PA1010, viscosity number 135 ± 30 ml / L, melting point 167°C as measured by DSC (second scan).

[0154] Terpo PA Type A from Sailuoluo (Shanghai): Based on a copolymer of PA6, PA66, and PA1010 in weight ratios of 10% / 20% / 70%, with melting points ranging from 145°C to 155°C, several melting peaks (DSC, first scan), and a melting point of 144°C (DSC, second scan). DSC was obtained using a Netzsch DSC 204 F1 (10 K / min). The amide frequency was calculated to be 10.7.

[0155] PBT: Pocan® B 1000 from Lanxess, with a 45 cm thickness at 250°C and 2.16 kg. 3 Thermoplastic polyester with a melt volume rate of 10 min and a melt temperature of 225°C.

[0156] Skypel G140D: A thermoplastic polyester elastomer from SK Chemicals based on PBT and butanediol polyether soft blocks, with a hardness ShD 40 (maximum) of 37 (15 s), a melt temperature of 157°C, and a melt flow rate of 7 g / 10 min at 190°C (2.16 kg).

[0157] Skypel G155D: A thermoplastic polyester elastomer from SK Chemicals based on PBT and butanediol polyether soft blocks, with a hardness ShD 55, a melt temperature of 202°C, and a melt flow rate of 11 g / 10 min at 220°C (2.16 kg).

[0158] PVDF: Kynar® HSV 900, a high molecular weight polyvinylidene fluoride homopolymer supplied by Arkema, GPC shows peaks at Mw at 93 kDa and 1.37 kDa (Z. Chen et al., Chem. Eng. J. 276 (2015) 174-184).

[0159] PVDF: Solef® 5130 from Solvay, which is PVDF modified with polar functional groups, with a molecular weight of 1 million to 1.1 million Daltons.

[0160] Active material LFP: Carbon-coated nano-sized LiFePO4, from Shenzhen Dynanonic's DY-11

[0161] Conductive carbon black: Super C® Li, from Timcal, BET 62 m 2 / g, ash content 0.010%

[0162] Conductive carbon black Super P, from Imerys.

[0163] Active material NCM: NCM (Ni-Co-Mn) 523 type, from BASF China.

[0164] Unless otherwise specified, all material contents given as % should be defined as wt.-%.

[0165] A general method for preparing blends of HNBR and polyamide or polyester in an internal mixer.

[0166] Typically, the following methods, which are described using polyamide, can be applied to polyester in a corresponding manner.

[0167] Before use, store the polyamide at 80°C for 16 hours. The melting point of the polyamide was determined by DSC. PA 6 polyamide was supplied by Lanxess as Durethan® B31 F. Initially, load the polyamide into the internal mixer. Before feeding, heat the internal mixer to 200°C, and after feeding, adjust the rotor speed to at least reach the melting temperature of the polyamide (230°C in this case). After one minute, add the HNBR rubber and aging stabilizer. Mix under temperature control, maintaining the mixture at a temperature of at least 230°C for 10 minutes. After one minute, vent the internal mixer and clean the shaft. Thereafter, vent the internal mixer to obtain the mixture.

[0168] A general method for preparing blends of HNBR and polyamide in a twin-screw extruder, I

[0169] Ground HNBR and PA6 granules were fed into a twin-screw extruder (Leistritz 27 Maxx, 48 D, screw diameter 28 mm). The temperature profile was adjusted to reach 240°C by setting the screw speed and barrel temperature. The throughput was 40 kg / h and the screw speed was 200 rpm.

[0170] The mixture is extruded through a die and granulated underwater, then quickly sieved and dried in air.

[0171] A general method for preparing blends of HNBR and polyamide in a twin-screw mini extruder with internal circulation, II

[0172] HNBR cut into small pieces and polyamide resin (10 wt.-%) were melt-blended using a conical, upright micro-twin-screw extruder, available from Explore as a micro-blender MC15 HT with a 15 ml internal volume. The material was fed into the hopper via a piston and melt-blended through internal circulation to simulate continuous, large-scale twin-screw extruder operation. PA was first introduced into the mixer and mixed for 1 minute, followed by the introduction of HNBR and mixing for another 5 minutes.

[0173] Composite material preparation test

[0174] Composite Material Test 1: HNBR 1 (100 phr) and PA 6 (10 phr) were melt-blended using the twin-screw extruder method I described above to obtain composite material 1 in granular form. The melt peak of PA 6 in the composite material was determined to be 217°C (second heating, DSC). The melt peak of PA 6 before blending was determined to be 221°C (DSC). The unit phr refers to 100 parts of rubber.

[0175] Composite material test 2: HNBR 1 (100 phr) and PA 6 (50 phr) were melt-blended using the twin-screw extruder method I described above to obtain composite material 2 in granular form.

[0176] Composite Material Test 3: HNBR 3 (90%) and terpo PA ZN150 (10%) were melt-blended using a twin-screw extruder, Method II, to obtain composite material 3 in granular form. The melt temperature was 180°C. Units % refer to 100% of the total amount of the blend.

[0177] Composite Material Test 4: HNBR 3 (90%) and terpo PA Type A (10%) were melt-blended using twin-screw extruder method II to obtain composite material 4 in granular form. The melt temperature was 180°C.

[0178] Composite Material Test 5: HNBR 3 (90%) and PA6 (10%) were melt-blended using twin-screw extruder method II to obtain composite material 5 in granular form. The melt temperature was 230°C.

[0179] Composite material test 6: HNBR 4 (100 phr) and PA6 (10 phr) were melt-blended using twin-screw extruder method I to obtain composite material 6 in granular form.

[0180] Composite material test 7: HNBR 4 (100 phr) and PA6 (50 phr) were melt-blended using twin-screw extruder method I to obtain composite material 7 in granular form.

[0181] Blend Test 8: HNBR 4 (90 wt.-%) and PA6 (10 wt.-%) were melt-blended using a twin-screw extruder, Method II. Melt temperatures were varied from 230°C to 220°C, 210°C, 200°C, and 190°C in a series of individual tests, where each blend was taken as a sample and its solubility in NMP was evaluated. It was observed that the samples taken from the mixer were all homogeneous, while those with higher temperatures tended to have a glossier surface. Surprisingly, all samples were soluble in NMP. However, for low solution viscosity, higher melt mixing temperatures should be preferred. In the case of PA6 as the modified resin, the temperature should not be lower than 210°C, or not lower than approximately 15°C below the DSC melt peak.

[0182] Composites 9 to 12: HNBR 5 and PA 6 were melt-blended using a twin-screw extruder, method II, at 230°C, with PA 6 contents of 10% and 30%, respectively. These experiments were then repeated using terpo PA type A and a melt temperature of 180°C. In this way, composites 9 and 10 were obtained, and then composites 11 to 12 were obtained. These blends appeared to be homogeneous.

[0183] Attempts were made to dissolve these composite materials in NMP; however, undissolved particles remained in the solution after 7 days. The conclusion was that the compatibility of this HNBR matrix with the PA resin was insufficient to allow for the formation of a stable dispersion in NMP.

[0184] Composite Material Test 13: HNBR 4 (90 wt.-%) and PBT (dried at 100°C for 2 h) were melt-blended using a twin-screw extruder, Method II. The mixing temperature was 230°C. The extruded strips were uniform and had a smooth surface.

[0185] Composite Material Test 14: HNBR 4 (90 wt.-%) and Skypel G140D (dried at 100°C for 2 h) were melt-blended using a twin-screw extruder, Method II. The mixing temperature was 165°C–167°C. The extruded strips were uniform and had a smooth surface.

[0186] Composite Material Test 15: HNBR 4 (90 wt.-%) and Skypel G155D (dried at 100°C for 2 h) were melt-blended using a twin-screw extruder, Method II. The mixing temperature was 213°C. The extruded strips were uniform and had a smooth surface.

[0187] Mechanical properties of adhesive composites

[0188] Stress-strain curves were obtained from the pressed samples of composite material test 2. These curves show that, relative to pure HNBR, the composite material of the present invention exhibits an increase in modulus at lower elongation. Such curves... Figure 1 As shown in the figure, Figure 1 The stress-strain curves of the adhesive films of HNBR 1 and composite material 2 are shown in detail, with measurements taken for three corresponding samples (HT 1 to HT 3).

[0189] Preparation of composite material solutions in NMP

[0190] Polymer samples were cut into small pieces of approximately 1 cm and dried overnight in a vacuum oven at 50°C. These polymer fragments were then dissolved in dried NMP using a shaker bed at room temperature to obtain a homogeneous solution with a solids content of 8%. Composite samples were dried and dissolved in the same manner. The solutions were analyzed using a Brookfield rheometer, ranging from 1 to 1000 s over 700 s. -1 Shear scan and then rescan to 1 s -1 The solution viscosity was tested (flow profile) to check for any thixotropy. Particle size was tested using Malvern's ZetaSizer (laser correlation spectroscopy).

[0191] Composite material 1 provides solution 1, and HNBR 1 provides solution 2. In the case of PA6, no dissolution was observed, and the particles remained unswollen.

[0192] Solution 1 is slightly opaque compared to solution 2, which is based on pure HNBR and is clear. This indicates that PA is dispersed in the HNBR matrix in very small domains.

[0193] Furthermore, such as Figure 2 As shown, the corresponding flow curves are provided. In detail, Figure 2 Flow profiles are shown, which show composite test 1 (fresh composite with HNBR 1) and polymer HNBR 1, and a solution of composite test 1 after 7 days of storage (composite with HNBR 1 after 7 days).

[0194] like Figure 2 The flow profiles shown reveal that the addition of PA to HNBR (Composite Test 1) yields a lower viscosity across the entire shear range. The rheology did not change with solution storage, meaning the polymer is stable in solution, even though PA is immiscible with HNBR. The solution was assessed as stable as defined in the Molau test.

[0195] Furthermore, particle size distribution was observed; see [link to relevant documentation]. Figure 3 Specifically, according to Malvern, the particle size is approximately 550 nm. When the sample was examined using an atomic force microscope (AFM, a sample slicer cut at -190°C, by phase-contrast analysis), particles ranging from 1 micrometer to several hundred nm were visible. The arithmetic mean was 240 nm, and the volume fraction larger than 1 micrometer was only 18.1%. The largest particle found had a diameter of 1.01 micrometers.

[0196] To allow for stable resin dispersion when dissolving the composite material in the processing solvent, the particle size should not exceed 3 micrometers, and more preferably should be less than 2 micrometers. This can be ensured if the measured volume fraction of particles larger than 1 micrometer does not exceed 50% (determined via phase-contrast AFM). This analysis should be based on measurements of 40 and 10 μm particles. 2 Image evaluation.

[0197] Dissolution test was conducted using composite material 1 with MEK.

[0198] Composite material 1: 12.2% insoluble matter in methyl ethyl ketone (MEK) (according to DIN – ISO 17025), particle size D50% via AFM is 423 nm, composite material preparation details: 20 kg / h throughput, 200 rpm.

[0199] Composite material 1: 11.1% insoluble matter, particle size D50% via AFM is 409 nm, composite material preparation details: 40 kg / h throughput, 200 rpm.

[0200] Composite material 1: 12.5% ​​insoluble matter, particle size D50% via AFM is 412 nm, composite material preparation details: 60 kg / h throughput, 200 rpm.

[0201] HNBR 1: 0.6%, used for comparison

[0202] Dissolution tests showed that HNBR is soluble, with a very low content of insoluble matter. However, the composite material of the present invention has an insoluble matter content between 11.1% and 14.5%. Thermoplastic resin PA 6 is insoluble in MEK and is introduced into the composite material at 10 phr (equivalent to 9.1% by weight). Therefore, a small but significant excess of insoluble material can be designated as HNBR rubber associated with or combined with the thermoplastic resin. This can contribute to further stabilization of the dispersion.

[0203] Dissolution tests were conducted using composite materials 6 and 7 [Influence of PA content].

[0204]

[0205] Table 1

[0206] Composite 7 contained 50 phr of PA6 (33%) and was only partially dissolved in NMP. An attempt was made to dissolve 8% of PA6 in NMP on a shaker at room temperature. After several days, undissolved particles remained in the mixture. Shearing the mixture at 5,000 rpm using an IKA laboratory mixer produced a thick, white paste that remained heterogeneous. This led to the conclusion that the amount of PA6 dispersed in the composite (50 phr, 33 wt.%) was too high. Analysis of composite 7 via AFM revealed particle sizes of 3 micrometers and larger, which were closer to those of the composite containing only 10% PA6. This could explain why dissolution was no longer sufficiently good at such high PA contents.

[0207] The arithmetic mean of the particle size distribution in AFM was 503 nm, and the largest particle found in this analysis was 3.6 μm. This analysis was based on measurements of 40 and 10 μm particles. 2 Image evaluation. The volume fraction of particles larger than 1 micrometer is 74.3%, which makes it more likely that there are a significant number of larger particles.

[0208] Figure 4 Flow profiles of composite material 6 and HNBR 4 dissolved in NMP are further shown. The flow profile of composite material 6 shows a lower viscosity compared to pure HNBR 4. This may be related to the lower HNBR content in the polymer composite, or to shear-induced molecular weight degradation during composite preparation, or both.

[0209] HNBR 4 and its derived composites can be used to prepare dispersions of conductive carbon materials such as CNTs. It is anticipated that CNT pastes containing the composites of this invention will have lower viscosity compared to those containing pure HNBR (such as HNBR 4).

[0210] Meltdown test was conducted using composite material 8 [changes in processing temperature].

[0211] Figure 5 The flow curves are shown as the mixing temperature changes in Experiment 8 after dissolving in NMP (8%). Figure 6 The corresponding curves after 7 days of storage are shown. Mixing temperatures of 230°C and 220°C yield flow curves with very low thixotropy, while lower mixing temperatures result in higher thixotropy. These solutions show a moderate increase in viscosity after 7 days of storage. This indicates that the mixing temperature should not be too low below the melting point of the PA resin.

[0212] Figure 7 The variation of PA6 particle size with melt processing temperature in composite material 8 in NMP solution is further illustrated. According to the invention, the particle size discussed corresponds to the domain size of the condensate within the hydrogenated nitrile rubber matrix, which was also determined via AFM.

[0213] Dissolution tests were conducted using composite materials 9 to 12 [Influence of nitrile content on HNBR].

[0214] An attempt was made to dissolve 8 wt.% of the acrylonitrile in NMP at room temperature on a shaker. After 7 days, a significant amount of undissolved particles remained in the mixture. It was concluded that the selected HNBR grade with an acrylonitrile content of 28% was unsuitable for manufacturing NMP-soluble composites. Therefore, in the absence of additional functional groups in the HNBR, the acrylonitrile content should not be much lower than 34 wt.%, preferably not less than 30 wt.%.

[0215] Dissolution test using HNBR / polyester composite material

[0216] The composites from compounding tests 13 to 15 were dissolved in NMP to a concentration of 8 wt.-%. These composites dissolved completely, yielding an opaque solution. Figure 11As shown, composite 13 (with PBT) exhibits a flow profile with a lower viscosity compared to unmixed dissolved HNBR 4. Composite 15 (with Skypel G155D) shows a flow profile very similar to that of unmixed HNBR 4. In both cases, the viscosity remains stable after 7 days of storage. In the case of composite 14 (with Skypel G140D), the flow profile drifts to a higher viscosity; an increase in viscosity is observed after 7 days of storage. The viscosity follows a trend with the peak melt temperature of the polyester, as... Figure 12 As shown, the pair of entries with the lowest melting peak temperature corresponds to composite test 14 (with Skypel G140D), the pair of entries with the medium melting peak temperature corresponds to composite test 15 (with Skypel G155D), and the pair of entries with the highest melting peak temperature corresponds to composite test 13 (with PBT). To limit the viscosity of the dissolved polyester-containing composite, the melting temperature should be at 175°C, with an upper limit of 270°C, to avoid polymer degradation during melt mixing. Figure 12 The composite material 13 to 15 was dissolved in NMP, and the corresponding parameters were shown after mixing and storage for 7 days.

[0217] Solubility tests were conducted on composite materials 3, 4, and 5 in different battery process solvents to assess the solubility of polyamide resin.

[0218]

[0219] Table 2

[0220] Tests showed that the PA resins were insoluble in xylene or NMP. However, for composites 4 and 5, an opaque but homogeneous solution was obtained in xylene. For composite 3, the opaque solution in xylene still contained some gel particles. It is possible that complete dispersion could be achieved through shear treatment. These solutions do not exhibit thixotropy, therefore the shear history does not alter the rheology, which is favorable for coating applications.

[0221] Figure 8Flow profiles for composite materials 4 to 5 with a 10% solids content in xylene are shown. Specifically, solutions of composite materials 3 to 5 can be used as a binder to disperse the solid electrolyte to form a self-supporting sheet serving as an intermediate layer between the cathode and anode in a solid-state battery. An advantage of the composite materials of the present invention is that thermoplastic resins such as polyamides can be introduced together with HNBR to bind the solid electrolyte to the sheet, even if the resin is completely insoluble in the solvent. Careful selection of the coating solvent in the solid-state battery is necessary to ensure compatibility with the solid electrolyte, especially to avoid undesirable reactions with the solid electrolyte. The composite materials of the present invention are melt-blended to produce a dispersion in a soluble HNBR rubber matrix. Surprisingly, even when using xylene as a solvent, the thermoplastic resin, together with HNBR, forms a stable fine-particle dispersion in the solvent.

[0222] Preparation of cathode paste using LFP

[0223] The active materials LFP, DY 11, and conductive carbon black Super P were dried in an oven at 120°C for 2 hours. The binders HNBR and PVDF were dried in a vacuum oven at 120°C for 2 hours. All processing steps were performed in a drying chamber with a dew point not exceeding -54°C. The binder was dissolved in ½ of the total volume of dried NMP (shaker, room temperature), Super P was added, and then it was mixed at 2000 rpm for 12 minutes using a Thinky mixer (a planetary centrifugal mixer from Thinky Inc.). Then LFP was added with the remaining ½ NMP and further mixed in a Thinky mixer at 2000 rpm for 18 minutes. Then, additional NMP was added to achieve a final concentration of 10 s. --1 The viscosity was set at 8-10 Pa. All mixing steps were performed at 6-minute intervals, followed by cooling to room temperature. The cathode paste was then coated onto Al foil and PET film at 150 µm gauge, dried in a convection oven [120°C, 2 hours] for physical testing, dried in a vacuum oven [120°C, 4 hours] for impedance testing, and calendered using a 2-roll calender to reduce the thickness by approximately 50%.

[0224]

[0225] Table 3

[0226] Peel strength: Peel strength is determined by applying a 3M tape (1500 vinyl electrical tape) to the cathode and peeling the tape to achieve a geometry of approximately 180°, using the median peel strength value.

[0227] Flexibility: The coating flexibility is tested by winding the coated electrodes around a 2 mm diameter metal mandrel and visually observing for any cracks. Detected cracks are rated as poor; no cracks are rated as good. The mandrel test simulates the winding of combined electrodes from cylindrical and prismatic battery cells.

[0228] When in 10 s -1 When a viscosity of 8 to 10 Pa·s was used as a guide, Comparative Test 1 only achieved a cathodic paste solids content of 56%, while in Test 2, with HNBR 1, the solids content was already 66%. In Test 3, using composite material 1 as a binder, a solids content of 68% could be achieved. The peel strength value on Al-C was acceptable, although slightly lower for Test 3. In Tests 4 and 5, the binder dosage was reduced to 1.6%. The solids content could then be further increased to 68% and 70%, respectively. The solids content with composite material as a binder exceeded that with HNBR as a binder alone, which is the objective of this invention.

[0229] Surprisingly, when HNBR or the composite material of this invention is used at lower dosage levels, the peel strength values ​​even reach higher levels.

[0230] When the cathode flexibility was tested with a mandrel tester, the cathode of Comparative Test 1 with PVDF showed cracks and therefore failed the flexibility test.

[0231] Figure 9 Further details pertain to the rheological profiles of the slurry as outlined in Table 3 above.

[0232] Cathode slurry prepared using NCM

[0233] The slurries were prepared using experiments 6 to 8 in the same manner as LFP, but using PVDF Solef 5130 as the active material.

[0234]

[0235] Table 4

[0236] The total solids content is higher because NCM has a larger particle size compared to LFP. The PVDF-based slurry achieves a solids content of 72%, while the HNBR-based slurry reaches 78%. The slurry with composite adhesive 1 gives even 80% solids content, which is the objective of this invention. The peel strength values ​​are higher for both HNBR and the composite adhesive compared to PVDF.

[0237] Figure 10 Further details involve rheological flow profiles from experiments using NCM cathode slurry, as shown in Table 4.

Claims

1. An adhesive composite material for an electrode adhesive in an electrochemical energy storage device, the adhesive composite material containing... a) Hydrogenated nitrile butadiene rubber; and b) Condensation polymers selected from the group consisting of: polyamides having a melting point of 140°C to 270°C and polyesters having a melting point of 175°C to 270°C; wherein The condensation polymer forms domains in the hydrogenated nitrile butadiene rubber, wherein these domains have a size D50 of less than 3 micrometers within the matrix of the hydrogenated nitrile butadiene rubber.

2. The adhesive composite material according to claim 1, wherein, This hydrogenated nitrile butadiene rubber contains acrylate units, of which the sum of the remaining hydrocarbon-based monomer units is less than 70 wt.%.

3. The adhesive composite material according to any one of claims 1 or 2, wherein, The hydrogenated nitrile butadiene rubber has an acrylonitrile content of 7 to 55 wt.-% (e.g., 15 to 40 wt.-%) and a degree of hydrogenation of less than 1% as measured by RDB.

4. The adhesive composite material according to any one of claims 1 to 3, wherein, The content of condensation polymers is in the range of 5 to 40 phr, where 100 phr refers to the hydrogenated nitrile butadiene rubber.

5. The adhesive composite material according to any one of claims 1 to 4, wherein, The polyamide is polyamide 6.

6. The adhesive composite material according to any one of claims 1 to 5, wherein, The viscosity ratio of the HNBR to the condensation polymer is between 1.3 and 5.

7. The adhesive composite material according to any one of claims 1 to 6, wherein, The binder composite material is present in an electrode coating dispersion containing electrochemically active materials and conductive carbon materials dispersed in an organic solvent.

8. The adhesive composite material according to any one of claims 1 to 6, wherein, The binder composite material is present in an electrode coating dispersion containing a solid electrolyte dispersed in an organic solvent, optionally an electrochemically active material, and optionally a conductive carbon material.

9. The adhesive composite material according to any one of claims 1 to 8, wherein, The composite material is prepared by melt-mixing the condensation polymer and the hydrogenated nitrile rubber.

10. The adhesive composite material according to any one of claims 1 to 9, wherein, This adhesive composite material is free of halogenated compounds.

11. The adhesive composite material according to any one of claims 1 to 10, wherein, The adhesive composite material passed the selective dissolution Molau test.

12. An electrode for an electrochemical energy storage device, wherein the electrode comprises a binder composite material disposed according to any one of claims 1 to 11.

13. An electrochemical energy storage device, wherein the electrochemical energy storage device comprises an anode and a cathode, the cathode being provided according to claim 12.

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